Effects of hot water extraction pretreatment on physicochemical changes of Douglas fir

Hot water extraction (HWE) is an autocatalytic pretreatment that can be effectively integrated into most of the conversion technologies for extracting hemicelluloses from woody biomass. The objective of this study was to understand the influence of pretreatment factors on removal of hemicelluloses from Douglas fir chips. Compositional change in biomass was analyzed with ion chromatography and further confirmed with Fourier transform infrared spectroscopy (FT-IR). Highest hemicellulose extraction yield (HEY) was estimated to be 67.44% at the optimum reaction time (79 min) and temperature (180 °C) by using response surface methodology (RSM). Experimental results show that the HEY increased from 19.29 to 70.81% depending on the reaction time (30–120 min) and the temperature (140–180 °C). Effects of the severity factor (SF) on the mass removal and compositional changes were also evaluated. Hygroscopicity and thermal stability of wood were improved after HWE pretreatment. Colorimetric analysis showed that temperature has a greater influence on color of the wood chips during HWE pretreatment than dwell time. HWE pretreatment shows great potential for extracting hemicelluloses and altering physicochemical properties of wood in an integrated biorefinery for diversification of product portfolio.     

Comparison of black liquor gasification with other pulping biorefinery concepts – Systems analysis of economic performance and CO2 emissions

Black liquor gasification (BLG) is being developed as an alternative technology for energy and chemical recovery in kraft pulp mills. This study compares BLG – with downstream production of DME (dimethyl ether) or electricity – with recovery boiler-based pulping biorefinery concepts for different types of mills. The comparison is based on profitability as well as CO₂ emissions, using different future energy market scenarios. The possibility for carbon capture and storage (CCS) is considered. The results show that, if commercialised, BLG with DME production could be profitable for both market pulp mills and integrated pulp and paper mills in all energy market scenarios considered. Recovery boiler-based biorefinery concepts including extraction of lignin or solid biomass gasification with DME production could also be profitable for market and integrated mills, respectively. If the mill is located close to an infrastructure for CO₂ collection and transportation, CCS significantly improves profitability in scenarios with a high CO₂ emissions charge, for both combustion- and gasification-based systems. Concepts that include CCS generally show a large potential for reduction of global CO₂ emissions. Few of the concepts without CCS achieve a significant reduction of CO₂ emissions, especially for integrated mills.     

Energy and economic assessment of soda and organosolv biorefinery processes

Lignocellulosic biomass, particularly agricultural and forestry residues, is becoming a potential renewable energy and products source. Lignocellulosic biomass processing technologies include a primary separation of its main constituents, cellulose, hemicelluloses and lignin, as well as further treatment and processing to obtain different platform chemicals to design consistently structured compounds as chemical building blocks. The economic competitiveness of the obtained products is highly dependent on the separation and purification technologies used and the process energetic efficiency. For this proposal, process simulation tools are very useful to design a competitive and effective biorefinery scheme. In the present work, the energetic and economical efficiencies of two biorefinery processes, soda and organosolv-ethanol systems, were analyzed using the simulation software Aspen Plus^®. The process design consisted of several units (reaction, solid fraction washing, products recovery and liquid fraction processing). Mass and energy balances were established and both systems were compared in terms of yield, solvents/reactants recovery and energy consumption. Aspen HX-Net software was used to analyze the process heat exchange network in order to improve energy consumptions. The development of rigorous simulations allowed to determine the economical feasibility of both biorefinery schemes, and to establish the most appropriate operation conditions for both processes.     

Thermogravimetric analysis as a new method to determine the lignocellulosic composition of biomass

Biomass energy uses organic matter such as wood or plants - lignocellulosic biomass - for creating heat, generating electricity and producing green oil for cars. Modern biomass energy recycles organic leftovers from forestry and agriculture, like corn stovers, rice husks, wood waste and pressed sugar cane, or uses special, fast-growing “energy crops” like willow and switchgrass, as fuel. Biomass is composed of three major components: cellulose, hemicelluloses, and lignin. Their differences in chemical structures lead to different chemical reactivities, making the relative composition in cellulose, hemicelluloses and lignin in the biomass a crucial factor for process design. In this paper thermogravimetric analysis is investigated as a new method to obtain lignin, hemicellulose and ??-cellulose contents in biomass. It is shown that this alternative method lead to comparable results than common methods used for the determination of the ??-cellulose content, with an enhancement of the accuracy in the determination of the hemicellulose content. Unfortunately, this method cannot be adopted for the determination of the lignin amount.     

The effect of long lead times for planning of energy efficiency and biorefinery technologies at a pulp mill

The pulp and paper industry has many promising opportunities in the biorefinery field. To reach this potential, investments are required in new, emerging technologies and systems solutions which cannot be quickly implemented. In this paper, an approach to model the necessarily long planning times for this kind of investments is presented. The methodology used is based on stochastic programming, and all investments are optimized under uncertain energy market conditions. The uncertain cost development of the emerging technologies is also considered. It is analyzed using scenario analysis where both the cost levels and the timing for market introduction are considered. The effect of long lead times is studied by assuming that no investments can be decided on now and implemented already today, and only investments planned for today can be implemented in, for example, five years. An example is presented to illustrate the usefulness of the proposed approach. The example includes the possibility of future investment in lignin separation, and shows how the investment planning of industrial energy efficiency investments can be guided by using the proposed systematic approach. The example also illustrates the value of keeping flexibility in the investment planning.     

Energy efficiency investments in Kraft pulp mills given uncertain climate policy

Energy efficiency measures in pulp mills can potentially reduce the consumption of biofuel, which can instead be exported and used elsewhere. In this paper a methodology is proposed for analysing the robustness of energy efficiency investments in Kraft pulp mills or other industrial process plants equipped with biofuelled combined heat and power units, given uncertain future climate policy. The outlook for biofuel and electricity prices is a key factor for deciding if energy efficiency measures are cost competitive. CO ₂ emission charges resulting from climate policy are internalized and thus included in electricity and biofuel prices. The proposed methodology includes a price-setting model for biofuel that assumes a constant price ratio between biofuel and electricity in the Nordic countries. Thirteen energy efficiency retrofit measures are analysed for an existing Swedish Kraft pulp mill. Special attention is paid to heat-integrated evaporation using excess process heat. Four possible energy market development paths are considered that reflect different climate policies. Pulp mill energy efficiency investments considered are shown to be robust with respect to uncertain climate policy. Copyright © 2006 John Wiley & Sons, Ltd.     

Life cycle assessment of SNG from wood for heating, electricity, and transportation

The conversion of wood to synthetic natural gas (SNG) via gasification and catalytic methanation is a renewable close to commercialization technology that could substitute fossil fuels and alleviate global warming. In order to assure that it is beneficial from the environmental perspective, a cradle to grave life cycle assessment (LCA) of SNG from a first-of-its-kind polygeneration unit for heating, electricity generation, and transportation was conducted. These SNG systems were compared to fossil and conventional wood reference systems and environmental benefits from their substitution evaluated. Finally, we conduct sensitivity analysis for expected technological improvements and factors that could decrease environmental performance.It is shown that substituting fossil technologies with SNG systems is environmentally beneficial with regard to global warming and for selected technologies also with regard to aggregated environmental impacts. On the condition that process heat is used efficiently, technological improvements such as increased efficiency and denitrification could further increase this advantage. On the other hand, lower GHG emissions and aggregated impacts are partly compensated by other environmental effects, e.g. eutrophication, ecotoxicity, and respiratory disease caused by inorganics. Since more efficient alternatives exist for the generation of heat and electricity from wood, it is argued that SNG is best used for transportation. In the light of a growing demand for renewable transportation fuels and commercial scale technological development being only in its initial stage, the production of SNG from wood seems to be a promising technology for the near future.     

Heat integrated heat pumping for biomass gasification processing

The main part of this paper is an industrial case study. It deals with an application of a heat pump in energy systems for biomass gasification in a wood processing plant. Process integration methodology is applied to deal with complex design interactions as many streams requiring heating and cooling are involved in the energy recovery. A refrigeration cycle maintains low temperature in the scrubber where the production gas (or synthesis gas–syngas) is cooled and undesirable contaminants are removed before the syngas is introduced into the engine. In addition to electricity generation, a large amount of waste heat is available in the biomass gasification system studied in the paper, and its appropriate heat integration with utility systems within a plant allows the available heat to be efficiently utilized for the site. The conceptual understanding gained from the case study provides systematic design guidelines for further process development and industrial implementation in practice.     

A comprehensive review on lignocellulosic biomass biorefinery for sustainable biofuel production

The increasingly severe environmental pollution and energy shortage issues have demanded the production of renewable and sustainable biofuels to replace conventional fossil fuels. Lignocellulosic (LC) biomass as an abundant feedstock for second-generation biofuel production can help overcome the shortcomings of first-generation biofuels related to the “food versus fuel” debate and feedstock availability. Embracing the “circular bioeconomy” concept, an integrated biorefinery platform of LC biomass can be performed by employing different conversion technologies to obtain multiple valuable products. This review provides an overview of the principles and applications of thermochemical processes (pyrolysis, torrefaction, hydrothermal liquefaction, and gasification) and biochemical processes (pretreatment technologies, enzyme hydrolysis, biochemical conversion processes) involved in LC biomass biorefinery for potential biofuel applications. The engineering perspective of LC biofuel production on separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation (SSCF), and consolidated bioprocessing (CBP) were also discussed.     

Technical, economic and environmental analysis of energy production from municipal solid waste

Four technologies are investigated which produce energy from municipal solid waste (MSW): incineration, gasification, generation of biogas and utilisation in a combined heat and power (CHP) plant, generation of biogas and conversion to transport fuel.Typically the residual component of MSW (non-recyclable, non-organic) is incinerated producing electricity at an efficiency of about 20% and thermal product at an efficiency of about 55%. This is problematic in an Irish context where utilisation of thermal products is not the norm. Gasification produces electricity at an efficiency of about 34%; this would suggest that gasification of the residual component of MSW is more advantageous than incineration where a market for thermal product does not exist. Gasification produces more electricity than incineration, requires a smaller gate fee than incineration and when thermal product is not utilised generates less greenhouse gas per kWh than incineration. Gasification of MSW (a non-homogenous fuel) is, however, not proven at commercial scale.Biogas may be generated by digesting the organic fraction of MSW (OFMSW). The produced biogas may be utilised for CHP production or for transport fuel production as CH₄-enriched biogas. When used to produce transport fuel some of the biogas is used in a small CHP unit to meet electricity demand on site. This generates a surplus thermal product.Both biogas technologies require significantly less investment costs than the thermal conversion technologies (incineration and gasification) and have smaller gate fees. Of the four technologies investigated transport fuel production requires the least gate fee. A shortfall of the transport fuel production technology is that only 50% of biogas is available for scrubbing to CH₄-enriched biogas.     

The value of flexibility for pulp mills investing in energy efficiency and future biorefinery concepts

Changing conditions in biomass and energy markets require the pulp and paper industry to improve energy efficiency and find new opportunities in biorefinery implementation. Considering the expected changes in the pulp mill environment and the variety of potential technology pathways, flexibility should be a strong advantage for pulp mills. In this context, flexibility is defined as the ability of the pulp mill to respond to changing conditions. The aim of this article is to show the potential value of flexibility in the planning of pulp mill energy and biorefinery projects and to demonstrate how this value can be incorporated into models for optimal strategic planning of such investments. The paper discusses the requirements on the optimization models in order to adequately capture the value of flexibility. It is suggested that key elements of the optimization model are multiple points in time where investment decisions can be made as well as multiple scenarios representing possible energy price changes over time. The use of a systematic optimization methodology that incorporates these model features is illustrated by a case study, which includes opportunities for district heating cooperation as well as for lignin extraction and valorization. A quantitative valuation of flexibility is provided for this case study. The study also demonstrates how optimal investment decisions for a pulp mill today are influenced by expected future changes in the markets for energy and bioproducts. Copyright © 2014 John Wiley & Sons, Ltd.     

Dilute mixed-acid pretreatment of sugarcane bagasse for ethanol production

Integral utilisation of bagasse is a high priority for the diversification of the sugarcane industry. The application of a biorefinery philosophy to bagasse utilisation requires its fractionation into its main components: cellulose, hemicelluloses and lignin. The first stage in that process is the pretreatment, in which a considerable part of hemicelluloses is solubilised, and cellulose is activated towards enzymatic hydrolysis. In this work, a pretreatment method using a mixture of sulfuric and acetic acid is investigated. Two different solid-to-liquid ratios (1.5:10 and 1:10) were used in the pretreatment. Both conditions efficiently hydrolysed the hemicelluloses giving removals above 90%. The extractive components were also effectively solubilised, and lignin was only slightly affected. Cellulose degradation was below 15%, which corresponded to the low crystallinity fraction. The analysis of the morphology of pretreated bagasse confirmed the results obtained in the chemical characterization.     

Biomass Energy and Biochemical Conversion Processing for Fuels and Chemicals

Biomass, mainly in the form of wood, is the oldest form of energy used by humans. Biomass is used to meet a variety of energy needs, including generating electricity, heating homes, fueling vehicles, and providing process heat for industrial facilities. Biomass potential includes wood and animal and plant wastes. Biomass, mainly now represents only 3% of primary energy consumption in industrialized countries. World production of biomass is estimated at 146 billion metric tons a year, mostly wild plant growth. Energy from biomass fuels is used in the electric utility, lumber and wood products, and pulp and paper industries. Biomass conversion may be conducted on two broad pathways: chemical decomposition and biological digestion. The conversion technologies for utilizing biomass can be separated into four basic categories: direct combustion processes, thermochemical processes, biochemical processes, and agrochemical processes. Biological processes are essentially microbic digestion and fermentation.     

Systems analysis of integrating biomass gasification with pulp and paper production - Effects on economic performance, CO2 emissions and energy use

This paper evaluates system aspects of biorefineries based on biomass gasification integrated with pulp and paper production. As a case the Billerud Karlsborg mill is used. Two biomass gasification concepts are considered: BIGDME (biomass integrated gasification dimethyl ether production) and BIGCC (biomass integrated gasification combined cycle). The systems analysis is made with respect to economic performance, global CO₂ emissions and primary energy use. As reference cases, BIGDME and BIGCC integrated with district heating are considered. Biomass gasification is shown to be potentially profitable for the mill. The results are highly dependent on assumed energy market parameters, particularly policy support. With strong policies promoting biofuels or renewable electricity, the calculated opportunity to invest in a gasification-based biorefinery exceeds investment cost estimates from the literature. When integrated with district heating the BIGDME case performs better than the BIGCC case, which shows high sensitivity to heat price and annual operating time. The BIGCC cases show potential to contribute to decreased global CO₂ emissions and energy use, which the BIGDME cases do not, mainly due to high biomass demand. As biomass is a limited resource, increased biomass use due to investments in gasification plants will lead to increased use of fossil fuels elsewhere in the system.     

Isolation and cationization of hemicelluloses from pre-hydrolysis liquor of kraft-based dissolving pulp production process

Hemicelluloses are the main organics dissolved in the pre-hydrolysis liquor (PHL) of the kraft-based dissolving pulp production process. In this study, two methods were employed to isolate the hemicelluloses from industrial PHL samples. The results showed that the hemicelluloses, precipitated in ethanol after an acidification step (Method 2), had a very high brightness (83% ISO) and low lignin content (0.44%) compared with the hemicelluloses obtained by the direct precipitation in ethanol without the acidification (Method 1), which had a brightness of 17.2% ISO and a lignin content of 5.67%. Furthermore, the hemicelluloses isolated via Method 2 were rendered cationic by using glycidyltrimethylammonium chloride (GTMAC), and the process parameters for the cationization reaction were studied, including the water content, reaction temperature and time, molar ratio of GTMAC/hemicelluloses, and the sodium hydroxide dosage. The optimized conditions for the cationic modification were 35% water content, 5% sodium hydroxide (both based on the mass of hemicelluloses), 1 (mol) GTMAC/hemicelluloses ratio, 65 °C, and 4 h reaction time. Finally, the cationic hemicelluloses were characterized and compared with unmodified hemicelluloses using the FT-IR and NMR analyses.     

Towards optimal selective fractionation for Nordic woody biomass using novel amine–organic superbase derived switchable ionic liquids (SILs)

Improved fractionation process conditions for wood dissolution with switchable ionic liquids (SILs) were determined. The short time, high temperature (STHT) system was introduced as a selective and efficient way to extract components from lignocellulosic material. A SIL based on monoethanol amine (MEA) and 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) formed via coupling with SO₂, was applied as a solvent in a 1:3 weight ratio with water. In essence, selective dissolution of mainly lignin was achieved by means of the aqueous SIL at 160 °C (∼6.1 bar corresponding to the vapor pressure of water) in 2 h and in a pressure vessel, for both hard- and soft-wood. About 95 wt-% of wood lignin was extracted. The dissolved components in the spent SIL were recovered by the addition of an anti-solvent whereupon over 70% of the dissolved components were recovered; the recovered fraction contained 19 wt-% hemicellulose while the rest of the material was in essence lignin. The non-dissolved, fluffy material contained ∼70 wt-% cellulose and ∼20 wt-% hemicellulose – a consistency resembling that of Kraft pulp.     

Investments into forest biorefineries under different price and policy structures

Increasing scarcity of oil reserves and the high CO₂ emissions from using oil have contributed to the development of renewable biofuels. Pulp and paper mill integrated forest biorefineries offer one important means to increase biofuel production. This study analyzes the effects of policies to support biofuel production in the pulp and paper sector. We study the relative effectiveness of three biofuel supporting policy instruments, namely production subsidy, input subsidy and investment subsidy. We present a partial equilibrium pulp and paper market model with a biorefinery investment option. A numerical model is used to evaluate the impacts of policy instruments on wood prices, as well as input choices and investment strategies of pulp and paper industries. The data represent the Finnish pulp and paper sector. We evaluate the values and direct costs of the policy instruments in a situation of exogenous biofuel production targets. The direct costs of input and investment subsidies are higher than those of a production subsidy. With all the policy instruments, Finnish pulp and paper mills would invest in wood-gasifying technology, instead of black liquor based one. The number of biorefinery units is dependent on the subsidy type — investment and input subsidies are likely to result in more numerous but smaller biofuel production units than a production subsidy. With all the policy instruments the demand for wood increases in Finland leading to higher wood prices. This, in turn, could reflect negatively on the profitability of the pulp and paper industries. To a significant degree, the model and the results can be generalized to other countries and markets where integrated pulp and paper mills are operating.     

An innovative biomass gasification process and its coupling with microturbine and fuel cell systems

The use of biomass, wood in particular, is one of the oldest forms of producing energy for heating or cooking. Nowadays, new technologies concerning the utilisation of biomass or waste residues are in demand and the trend to use them in decentralised applications for combined heat and power (CHP) production provides an attractive challenge to develop them. At the TU München an innovative allothermal gasification technology, the Biomass Heatpipe Reformer (BioHPR) has been developed. The aim of this project was to integrate the technology of liquid metal heatpipes in the gasification process in order to produce a hydrogen rich product gas from biomass or residues. The gasification product can be further used in microturbine or SOFC systems. The present paper presents the aforementioned gasification technology, its coupling with innovative CHP systems (with microturbine or fuel cells) and investigates, through the simulation of these systems, the optimum conditions of the integrated systems in order to reach the highest possible efficiencies.     

Comparison of options for utilization of a potential steam surplus at kraft pulp mills—Economic performance and CO2 emissions

This paper compares different energy‐related investment options that can be implemented in a kraft pulp mill with a potential steam surplus. The options investigated include lignin extraction, electricity production, capturing of CO₂ and black liquor gasification with production of electricity or biofuels, here DME. The investment options are compared with respect to annual net profit and global CO₂ emissions for different future energy market scenarios. A further analysis of how different parameters such as policy instruments and investment costs affect the different technologies also is included. The results show that, generally, for reasonable levels of biofuel support, the best economic performance among the studied technologies is achieved by extraction of lignin valued as oil. However, if the level of support for biofuels is high, black liquor gasification with DME production generally has the best economic performance among the studied options. All the investment options investigated decrease global CO₂ emissions significantly. Capturing and storing CO₂ from the recovery boiler flue gases result in the highest CO₂ emissions reduction and also is an economically attractive option in scenarios with a high CO₂ emissions charge. Copyright © 2012 John Wiley & Sons, Ltd.     

Gasification efficiencies of cellulose,hemicellulose and lignin fractions of biomass in aqueous media by using Pt on activated carbon catalyst

The diversity in the chemical composition of lignocellulosic feedstocks can affect the conversion technologies employed for biofuel production. Aqueous-phase reforming (APR) activities of cellulose, hemicellulose and lignin components of lignocellulosic biomass materials were evaluated for production of hydrogen content gas mixture using platinum catalyst on activated carbon support. Wheat straw, an abundant by-product from wheat production and kenaf (Hibiscus cannabinus L.), an annual herbaceous plant growing very fast with low lodging susceptibility were used as lignocellulosics in the present study. The hydrolysates of cellulose fractions of biomass materials showed the best performance for gasification. The results indicated that hemicellulose isolated from kenaf was more sensitive to degradation and therefore, produced more gaseous products than that of wheat straw. The hemicellulose isolated from kenaf biomass left the lowest amount of ungasified solid residue in APR among other cellulose and hemicellulose materials studied. Lignin fractions of both biomass materials were not reactive in APR to produce hydrogen rich gas mixture.Gasification efficiencies of kenaf and wheat straw's hemicelluloses were also compared with xylans from beechwood and oat spelts which were commercially available as hemicellulosic fractions.Oat spelts xylan showed better reforming activity over the beechwood xylan.